In certain practical applications, it is necessary to use mobile elements, such as structures enabling overland communication paths to overcome obstructions, mobile barriers, gates, walls of various kinds serving specific functional purposes, such as temporarily isolating a particular area, modifying the course of a fluid by channeling it in a given direction, preventing or at least containing the passage of a fluid into a given area, and so on. For such purposes, mobile elements are generally connected, e.g. by hinged means, to a supporting or anchoring structure and then, when needed, they are moved by suitable means so as to bring them into the required working position, e.g. by transferring them or, more commonly, by rotating them around the hinged axis. In many cases, such maneuvers are conducted only for a limited period of time and not necessarily with a regular frequency, and often also with very lengthy intervals between one maneuver and the next, so the mobile elements may remain at rest for the majority of their working life.
It is consequently clear that, in such contexts, it is essential to have suitable control devices installed together with the mobile elements to enable the actual working efficiency of the latter to be kept under control, and particularly to make sure that, in the event of their being moved, the mobile elements will respond correctly, even after very lengthy periods of inactivity, and move into the required position. In addition to the above-mentioned fundamental control function, these devices must also be capable of meeting further requirements dictated by the working conditions in which the mobile elements, with which they are associated, are operated, such as a resistance to mechanical or thermal stresses, a sufficiently long working life, the capacity to work in variable ambient conditions and to withstand aggressive elements, reliability, capacity for local and particularly for remote communication, minimal servicing demands, and so on.